U.S. patent application number 14/264393 was filed with the patent office on 2014-11-13 for touch type input device and method for detecting touching of touch panel.
This patent application is currently assigned to SMK CORPORATION. The applicant listed for this patent is KABUSHIKI KAISHA TOKAI RIKA DENKI SEISAKUSHO, SMK CORPORATION. Invention is credited to Syogo YAMAGUCHI, Osamu YOSHIKAWA.
Application Number | 20140333576 14/264393 |
Document ID | / |
Family ID | 50630690 |
Filed Date | 2014-11-13 |
United States Patent
Application |
20140333576 |
Kind Code |
A1 |
YAMAGUCHI; Syogo ; et
al. |
November 13, 2014 |
TOUCH TYPE INPUT DEVICE AND METHOD FOR DETECTING TOUCHING OF TOUCH
PANEL
Abstract
A touch type input device includes a touch panel having a sensor
array of drive electrodes and sensor electrodes. Capacitors are
formed at intersections of the drive electrodes and the sensor
electrodes. A controller determines whether or not a conductive
foreign matter exists on the touch panel from raw data values
indicating a change amount in the capacitance of each capacitor
from an initial reference value. Further, the controller determines
whether or not the touch panel has been touched from control data
values indicating a change amount in the capacitance of each
capacitor from a control reference value that is changed for each
capacitor in accordance with whether or not the foreign matter
exists. When the raw data values indicate the existence of the
foreign matter, the controller sets the control reference value of
each capacitor to a raw data reference value corresponding to the
present raw data value.
Inventors: |
YAMAGUCHI; Syogo; (Aichi,
JP) ; YOSHIKAWA; Osamu; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOKAI RIKA DENKI SEISAKUSHO
SMK CORPORATION |
Aichi
Tokyo |
|
JP
JP |
|
|
Assignee: |
SMK CORPORATION
Tokyo
JP
KABUSHIKI KAISHA TOKAI RIKA DENKI SEISAKUSHO
Aichi
JP
|
Family ID: |
50630690 |
Appl. No.: |
14/264393 |
Filed: |
April 29, 2014 |
Current U.S.
Class: |
345/174 |
Current CPC
Class: |
G06F 3/0446 20190501;
G06F 3/0445 20190501; G06F 3/04186 20190501; G06F 3/04182
20190501 |
Class at
Publication: |
345/174 |
International
Class: |
G06F 3/041 20060101
G06F003/041; G06F 3/044 20060101 G06F003/044 |
Foreign Application Data
Date |
Code |
Application Number |
May 10, 2013 |
JP |
2013-100445 |
Claims
1. A touch type input device comprising: a touch panel including a
sensor array and an operation surface, wherein the sensor array
includes drive electrodes and sensor electrodes insulated from and
stacked on the drive electrodes, wherein the drive electrodes and
the sensor electrodes are arranged in a grid-shaped pattern that
forms capacitors at intersections of the drive electrodes and the
sensor electrodes; and a controller that applies a drive signal to
the drive electrodes and detects touching of the operation surface
of the touch panel from changes in capacitance of each capacitor,
wherein the controller is configured so that the controller
determines whether or not a conductive foreign matter exists on the
operation surface from raw data values indicating a change amount
in the capacitance of each capacitor from an initial reference
value that is set in advance for each capacitor, the controller
determines whether or not the operation surface has been touched
from control data values indicating a change amount in the
capacitance of each capacitor from a control reference value that
is changed for each capacitor in accordance with whether or not the
conductive foreign matter exists, when the controller determines
from the raw data values that the conductive foreign matter exists
on the operation surface, the controller sets the control reference
value of each capacitor to a raw data reference value corresponding
to the present raw data value, and when the controller determines
from the raw data values that the conductive foreign matter does
not exist on the operation surface, the controller sets the control
reference value of each capacitor to the initial reference
value.
2. The touch type input device according to claim 1, wherein the
controller is further configured so that when the controller
determines from the raw data values that the conductive foreign
matter exists on the operation surface, the controller determines
whether or not a further conductive foreign matter exists on the
operation surface from the control data values, when the controller
determines from the control data values that the further conductive
foreign matter exists on the operation surface, the controller sets
the control reference value of each of the capacitors to a control
data reference value corresponding to the present control data
value, and when the controller determines from the control data
values that the further conductive foreign matter does not exist on
the operation surface, the controller sets the control reference
value of each of the capacitors to the raw data reference value
corresponding to the capacitor.
3. A method for detecting touching of a touch panel regardless of
the existence of a conductive foreign matter on the touch panel,
wherein the touch panel includes a sensor array and an operation
surface, the sensor array includes drive electrodes and sensor
electrodes insulated from and stacked on the drive electrodes, the
drive electrodes and the sensor electrodes are arranged in a
grid-shaped pattern that forms capacitors at intersections of the
drive electrodes and the sensor electrodes, the method comprising:
applying a drive signal to the drive electrodes; detecting
capacitance of each capacitor from a charge-discharge current
flowing through a corresponding one of the sensor electrodes in
accordance with the drive signal applied to a corresponding one of
the drive electrodes; and detecting touching of the operation
surface of the touch panel from changes in capacitance of each
capacitor, the detecting touching of the operation surface
including determining whether or not a conductive foreign matter
exists on the operation surface from raw data values indicating a
change amount in the capacitance of each capacitor from an initial
reference value that is set in advance for each capacitor,
determining whether or not the operation surface has been touched
from control data values indicating a change amount in the
capacitance of each capacitor from a control reference value that
is changed for each capacitor in accordance with whether or not the
conductive foreign matter exists, when the raw data values indicate
the existence of the conductive foreign matter on the operation
surface, setting the control reference value of each capacitor to a
raw data reference value corresponding to the present raw data
value, and when the raw data values do not indicate the existence
of the conductive foreign matter on the operation surface, setting
the control reference value of each capacitor to the initial
reference value.
4. The method according to claim 3, wherein the detecting touching
of the operation surface further includes when the raw data values
indicate the existence of the conductive foreign matter on the
operation surface, determining whether or not a further conductive
foreign matter exists on the operation surface from the control
data values, when the control data values indicate the existence of
the further conductive foreign matter on the operation surface,
setting the control reference value of each capacitor to a control
data reference value corresponding to the present control data
value, and when the control data values do not indicate the
existence of the further conductive foreign matter on the operation
surface, setting the control reference value of each capacitor to
the raw data reference value corresponding to the capacitor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2013-100445,
filed on May 10, 2013, the entire contents of which are
incorporated herein by reference.
FIELD
[0002] The present invention relates to a touch type input device
and a method for detecting touching of a touch panel.
BACKGROUND
[0003] Japanese Laid-Open Patent Publication No. 2010-9321
describes a touch type input device including a touch panel that is
touched to operate virtual buttons shown on a display. In the touch
type input device, for example, a user touches an operation surface
of the touch panel to select one of a plurality of functional items
shown on the display. This allows the user to view the desired
interface on the display or operate an onboard device. Such
touching of the touch panel includes, in addition to a simple touch
of the operation surface, swiping or flicking of the operation
surface in which a finger is moved along the operation surface in a
single direction. For example, by swiping or flicking the operation
surface, the interface shown on the display is scrolled.
[0004] Such a touch panel may implement projected capacitive
technology. A projected capacitance type touch panel includes drive
electrodes and sensor electrodes that are arranged in a grid-shaped
pattern. Capacitors are formed at the intersecting points of the
drive electrodes and the sensor electrodes. Touching of the touch
panel is detected from the capacitance of each capacitor. A mutual
capacitance type touch panel detects a touched position based on
changes in the capacitance of each capacitor. The mutual
capacitance type touch panel is advantageous in that a number of
touch positions may be simultaneously detected.
[0005] A conductive foreign matter such as a water droplet or a
coin may contact or collect on the operation surface of the touch
panel. The contact of such a foreign matter needs to be
distinguished from a finger that touches the operation surface. In
a mutual capacitance type touch panel, when a finger contacts the
operation surface, the capacitance of each capacitor in the area
touched by the finger changes from a reference value (zero), which
corresponds to a condition in which there is no object contacting
the operation surface, toward a first polarity side (e.g.,
positive). In contrast, when a foreign matter contacts the
operation surface, the capacitance of each capacitor in the area
that is in contact with the foreign matter changes toward a second
polarity side (e.g., negative), and the capacitance of each
capacitor in the area around the foreign matter changes toward the
first polarity side. Japanese Patent No. 4994489 describes a touch
type input device that takes this into consideration. The touch
type input device computes the distribution of the amount of change
in capacitance of the capacitors. When the peak value of the
changed amount distribution is less than or equal to a
predetermined negative threshold, the touch type input device
determines that a foreign matter is contacting the operation
surface.
[0006] When a conductive foreign matter remains in contact with the
operation surface of the touch panel, the capacitance of each
capacitor remains changed from the reference value. This hinders
the detection of a touch. Thus, the touch type input device of
Japanese Patent No. 4994489 shows a message on a display to prompt
the user to remove the foreign matter from the touch panel.
[0007] However, in the touch type input device described above, the
conductive foreign matter has to be removed from the operation
surface to allow for detection of the touching of the operation
surface. This is inconvenient, especially, when the touch type
input device is installed in a vehicle and a foreign matter cannot
be readily removed from the operation surface.
SUMMARY
[0008] One aspect of the present invention is a touch type input
device. The touch type input device includes a touch panel. The
touch panel includes a sensor array and an operation surface. The
sensor array includes drive electrodes and sensor electrodes
insulated from and stacked on the drive electrodes. The drive
electrodes and the sensor electrodes are arranged in a grid-shaped
pattern that forms capacitors at intersections of the drive
electrodes and the sensor electrodes. The touch type input device
further includes a controller that applies a drive signal to the
drive electrodes and detects touching of the operation surface of
the touch panel from changes in capacitance of each capacitor. The
controller determines whether or not a conductive foreign matter
exists on the operation surface from raw data values indicating a
change amount in the capacitance of each capacitor from an initial
reference value that is set in advance for each capacitor. The
controller determines whether or not the operation surface has been
touched from control data values indicating a change amount in the
capacitance of each capacitor from a control reference value that
is changed for each capacitor in accordance with whether or not the
conductive foreign matter exists. When the controller determines
from the raw data values that the conductive foreign matter exists
on the operation surface, the controller sets the control reference
value of each capacitor to a raw data reference value corresponding
to the present raw data value. When the controller determines from
the raw data values that the conductive foreign matter does not
exist on the operation surface, the controller sets the control
reference value of each capacitor to the initial reference
value.
[0009] Another aspect of the present invention is a method for
detecting touching of a touch panel regardless of the existence of
a conductive foreign matter on the touch panel, wherein the touch
panel includes a sensor array and an operation surface, the sensor
array includes drive electrodes and sensor electrodes insulated
from and stacked on the drive electrodes, the drive electrodes and
the sensor electrodes are arranged in a grid-shaped pattern that
forms capacitors at intersections of the drive electrodes and the
sensor electrodes. The method includes applying a drive signal to
the drive electrodes, detecting capacitance of each capacitor from
a charge-discharge current flowing through a corresponding one of
the sensor electrodes in accordance with the drive signal applied
to a corresponding one of the drive electrodes, and detecting
touching of the operation surface of the touch panel from changes
in capacitance of each capacitor. The detecting touching of the
operation surface includes determining whether or not a conductive
foreign matter exists on the operation surface from raw data values
indicating a change amount in the capacitance of each capacitor
from an initial reference value that is set in advance for each
capacitor, determining whether or not the operation surface has
been touched from control data values indicating a change amount in
the capacitance of each capacitor from a control reference value
that is changed for each capacitor in accordance with whether or
not the conductive foreign matter exists, when the raw data values
indicate the existence of the conductive foreign matter on the
operation surface, setting the control reference value of each
capacitor to a raw data reference value corresponding to the
present raw data value, and when the raw data values do not
indicate the existence of the conductive foreign matter on the
operation surface, setting the control reference value of each
capacitor to the initial reference value.
[0010] Other aspects and advantages of the present invention will
become apparent from the following description, taken in
conjunction with the accompanying drawings, illustrating by way of
example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention, together with objects and advantages thereof,
may best be understood by reference to the following description of
the presently preferred embodiments together with the accompanying
drawings in which:
[0012] FIG. 1 is a perspective view illustrating a touch type input
device installed in a vehicle;
[0013] FIG. 2 is a plan view illustrating an operation surface of a
touch panel on a center console;
[0014] FIG. 3 is a cross-sectional view of the touch panel taken
along line A-A in FIG. 2;
[0015] FIG. 4 is a schematic block diagram of the touch type input
device;
[0016] FIG. 5 is a flowchart illustrating the procedures for
detecting touching of the touch panel;
[0017] FIG. 6A is a schematic diagram illustrating the touch panel
when a conductive foreign matter is contacting the operation
surface;
[0018] FIG. 6B is a graph plotted from raw data values taken under
the condition illustrated in FIG. 6A;
[0019] FIG. 6C is a graph plotted from control data values taken
under the condition illustrated in FIG. 6A;
[0020] FIG. 7A is a schematic diagram illustrating the touch panel
when a finger touches a conductive foreign matter on the operation
surface;
[0021] FIG. 7B is a graph plotted from raw data values taken under
the condition illustrated in FIG. 7A;
[0022] FIG. 7C is a graph plotted from control data values taken
under the condition illustrated in FIG. 7A;
[0023] FIG. 8A is a schematic diagram illustrating the touch panel
when the operation surface is swiped with a finger that is in
contact with a conductive foreign matter on the operation
surface;
[0024] FIG. 8B is a graph plotted from raw data values taken under
the condition illustrated in FIG. 8A; and
[0025] FIG. 8C is a graph plotted from control data values taken
under the condition illustrated in FIG. 8A.
DESCRIPTION OF THE EMBODIMENTS
[0026] One embodiment of a touch type input device 5 will now be
described with reference to the drawings.
[0027] Referring to FIG. 1, a dashboard 1 includes a central
portion (center cluster) where a display 2 is set. A center console
3 includes a shift lever 4 and a touch type input device 5. The
touch type input device 5 includes a touch panel 11 that is set on
the center console 3 at the rear side of the shift lever 4. The
touch panel 11 includes an operation surface 11a. In the present
embodiment, the touch type input device 5 is installed in a vehicle
but may be installed in other machines. The operation surface 11a
is rectangular and substantially similar in shape to the display 2.
A user touches the operation surface 11a of the touch panel 11 with
a conductor, such as a finger or a stylus, to select the desired
functional item shown on the display 2 and accordingly operate an
onboard device, such as an air conditioner or a car navigation
system. Touching of the touch panel 11 includes, in addition to a
simple touch of the operation surface 11a, swiping or flicking of
the operation surface 11a in which a finger is moved along the
operation surface 11a in a single direction.
[0028] As illustrated in FIG. 2, the touch panel 11 includes a
sensor array 14. The sensor array 14 includes drive electrodes 12
and sensor electrodes 13, which are stacked on and insulated from
the drive electrodes 12. The drive electrodes 12 and the sensor
electrodes 13 are arranged in a grid-shaped pattern that forms
capacitors C (see FIG. 3) at the intersections of the drive
electrodes 12 and the sensor electrodes 13. For the sake of
brevity, FIG. 2 illustrates only seven of the drive electrodes 12
and five of the sensor electrodes 13.
[0029] Referring to FIG. 3, the drive electrodes 12 are arranged on
a drive substrate 15. The sensor electrodes 13 are arranged on a
sensor substrate 16, which is stacked on the drive substrate 15. A
cover 17 is set on the sensor substrate 16. The drive substrate 15,
the sensor substrate 16, and the cover 17 are each formed from an
insulative material, rectangular in shape, and larger than the
operation surface 11a. The cover 17 includes an upper surface that
partially forms the operation surface 11a of the touch panel
11.
[0030] The drive electrodes 12 and the sensor electrodes 13 are
each formed from strips of a conductive material. The drive
electrodes 12 are arranged parallel to one another extending in a
first direction (X direction) within the area of the drive
substrate 15 that corresponds to the operation surface 11a. The
sensor electrodes 13 are arranged parallel to one another extending
in a second direction (Y direction), which is orthogonal to the
first direction, within the area of the sensor substrate 16 that
corresponds to the operation surface 11a. Consequently, the drive
electrodes 12 and the sensor electrodes 13 form the sensor array
14, which has a grid-shaped pattern, in the operation surface 11a.
Further, as illustrated by the broken lines in FIG. 3, the
capacitors C are formed at intersections of the drive electrodes 12
and the sensor electrodes 13. In the present embodiment, an
adhesive agent 18 is used to fix the drive electrodes 12 to the
drive substrate 15 and the sensor electrodes 13 to the sensor
substrate 16.
[0031] As illustrated in FIG. 4, the touch type input device 5
further includes a controller 21 that applies a drive signal (pulse
signal) to the sensor array 14 to detect a touch, that is, touching
of the operation surface 11a of the touch panel 11. The controller
21 of the present embodiment employs the mutual capacitance
technology and detects a touched position based on a
charge-discharge current generated when the capacitance of each
capacitor C changes.
[0032] The controller 21 includes a drive unit 22, which is
connected to the drive electrodes 12, a detection unit 23, which is
connected to the sensor electrodes 13, and a control unit 24, which
controls the drive unit 22 and the detection unit 23. The drive
unit 22 selects the drive electrodes 12 one by one in response to
control signals from the control unit 24 and applies a drive signal
to the selected drive electrode 12. The detection unit 23 selects
the sensor electrodes 13 one by one in response to control signals
from the control unit 24 to receive the charge-discharge current
flowing through the selected sensor electrode 13 in accordance with
the drive signal applied to the selected drive electrode 12. The
detection unit 23 receives the charge-discharge current as an
output signal. Further, the detection unit 23 detects the
capacitance of each capacitor C based on the output signal from the
corresponding sensor electrode 13 and outputs a detection signal,
which indicates the capacitance of the capacitor C, to the control
unit 24. Then, the control unit 24 detects a touch and a touched
position (coordinates) from the detection signal and outputs the
detection result to the display 2.
[0033] The control unit 24 is capable of detecting a touch even
when a conductive foreign matter, such as a water droplet or a
coin, is contacting the operation surface 11a. In the present
embodiment, the capacitance of the capacitor C changes toward the
positive side when a finger or the like contacts the operation
surface 11a, and the capacitance changes toward the negative side
when a conductive foreign matter contacts the operation surface
11a.
[0034] The control unit 24 includes a memory 24a. The memory 24a
stores an initial reference value, which is set in advance for each
capacitor C. In the present embodiment, the initial reference value
is the capacitance when there is no object contacting the operation
surface 11a. That is, the initial reference value is set to 0
(zero). Further, the memory 24a stores a control reference value
for each capacitor C. The control reference value may be referred
to as a correction reference value. The control reference value of
each capacitor C is changed in accordance with whether or not a
foreign matter exists on the operation surface 11a of the touch
panel 11.
[0035] When the control unit 24 obtains the capacitance (detection
signal) of each capacitor C from the detection unit 23, the control
unit 24 determines whether or not a conductive foreign matter
exists on the touch panel 11, that is, whether or not a foreign
matter is contacting the operation surface 11a, based on raw data
values indicating the change amount in the capacitance of each
capacitor C from the initial reference value. For example, the
control unit 24 determines the existence of a foreign matter when
at least one of the raw data values is less than or equal to a
foreign matter determination threshold. The foreign matter
determination threshold is set to a predetermined negative value.
When the control unit 24 determines from the raw data values that a
foreign matter exists on the touch panel 11, the control unit 24
acquires the capacitance (detection signal) of each capacitor C
again from the detection unit 23. Then, the control unit 24
determines whether or not another conductive foreign matter exists
on the touch panel 11, that is, whether or not another foreign
matter is contacting the operation surface 11a, based on control
data values indicating the change amount in the capacitance of each
capacitor C from the control reference value. For example, the
control unit 24 determines the existence of a foreign material when
at least one of the control data values is less than or equal to
the foreign matter determination threshold. Further, the control
unit 24 determines whether or not the touch panel 11 has been
touched based on the control data values. For example, the control
unit 24 determines that the touch panel 11 has been touched when at
least one of the control data values is greater than or equal to a
touch determination threshold. The touch determination threshold is
set to a predetermined positive value. Of course, the control unit
24 can also determine whether or not the touch panel 11 has been
touched based on the raw data values.
[0036] When the control unit 24 determines from the raw data values
that a foreign matter exists on the operation surface 11a, the
control unit 24 sets the control reference value for each capacitor
C to the same value as the capacitance corresponding to the present
raw data value (hereafter, referred to as the raw data reference
value). In such a manner, when the control reference value is set
to the raw data reference value corresponding to the raw data value
of each capacitor C, the control unit 24 assumes that the
capacitance for each capacitor C is zero (0) under a situation in
which the foreign matter is in contact with the operation surface
11a. Then, the control unit 24 acquires control data values
indicating the change amount in the capacitance of each capacitor C
from the corresponding control reference value. When the control
unit 24 determines from the raw data values that there is no
foreign matter on the operation surface 11a, the control unit 24
sets the control reference value of each capacitor C as the initial
reference value.
[0037] Further, when the control unit 24 determines from the
control data values that a foreign matter exists on the operation
surface 11a, the control unit 24 sets a new control reference value
for each capacitor C to the same value as the capacitance
corresponding to the present control data value (hereafter,
referred to as the control data reference value). In such a manner,
when the control reference value is set to the control data
reference value corresponding to the control data value of each
capacitor C, the control unit 24 assumes that the capacitance for
each capacitor C is zero (0) under a situation in which the foreign
matter is in contact with the operation surface 11a. Then, the
control unit 24 acquires new control data values indicating the
change amount in the capacitance of each capacitor C from the
corresponding new control reference value. When the control unit 24
determines from the control data values that there is no foreign
matter on the operation surface 11a, the control unit 24 sets a new
control reference value to the raw data reference value for each
capacitor C. When the touch type input device 5 is activated, the
control reference values are set to the initial reference
values.
[0038] The procedures taken by the control unit 24 to detect
touching of the touch panel 11 will now be described with reference
to the flowchart of FIG. 5. The control unit 24 executes the
detection process in predetermined sampling cycles (detection
cycles) to detect touching of the touch panel 11.
[0039] When the control unit 24 receives a detection signal from
the detection unit 23 (step S1), the control unit 24 determines
from the raw data values whether or not a conductive foreign matter
exists on the operation surface 11a (step S2). When the control
unit 24 determines that a foreign matter exists on the operation
surface 11a (step S3: YES), the control unit 24 determines whether
or not a flag is set to indicate that the control reference value
differs from the initial reference value (step S4). The flag is
stored in the memory 24a. When the flag is not set (step S4: NO),
the control unit 24 sets the control reference value to the raw
data reference value for each capacitor C (step S5) and sets the
flag (step S6).
[0040] Then, the control unit 24 determines from the control data
values whether or not a conductive foreign matter exists on the
operation surface 11a (step S7). When the flag is set (step S4:
YES), the control unit 24 skips steps S5 and S6 and proceeds to
step S7 to perform a foreign matter determination based on the
control data values. When the control unit 24 determines that
another foreign matter exists on the operation surface 11a (step
S8: YES), the control unit 24 sets the control reference value to
the control data reference value for each capacitor C (step S9).
Then, the control unit 24 detects whether or not the touch panel 11
has been touched based on the control data values newly obtained
(step S10). When the control unit 24 determines from the control
data values that there is no foreign matter on the operation
surface 11a (step S8: NO), the control unit 24 skips step S9 and
proceeds to step S10 to detect touching of the touch panel 11 from
the control data values.
[0041] When the control unit 24 determines from the raw data values
that there is no foreign matter on the operation surface 11a (step
S3: NO), the control unit 24 sets the control reference value to
the initial reference value (step S11) and resets the flag (step
S12). Then, the control unit 24 proceeds to step S10 and detects
touching of the touch panel 11 from the control data values.
[0042] The detection of a touch when a foreign matter is contacting
the operation surface 11a of the touch panel 11 will now be
described.
[0043] Referring to FIGS. 6A and 6B, when a foreign matter contacts
the operation surface 11a of the touch panel 11, the raw data
values (capacitances of capacitors C) in the area contacting the
foreign matter are negative values. The raw data values around the
foreign matter are positive values. When each control reference
value is set to the initial reference value, the control data
values would be the same as the raw data values as illustrated by
the double-dashed line in FIG. 6C. To facilitate understanding,
FIGS. 6B and 6C use dots to show the raw data values and the
control data values obtained along a single line (X direction)
extending through the foreign matter. When a foreign matter exists
on the operation surface 11a as illustrated in FIG. 6A, at least
one of the raw data values is less than or equal to the foreign
matter determination threshold. Accordingly, the control unit 24
determines that a foreign matter exists on the operation surface
11a and sets each control reference value to the raw data reference
value, that is, the same value as the capacitance corresponding to
the present raw data value. When the capacitance of each capacitor
C is newly obtained under this situation, as illustrated by the
bold line in FIG. 6C, the control data value for each capacitor C
would be zero. Accordingly, if the touch panel 11 is touched under
a situation in which a foreign matter exists on the operation
surface 11a, the control data values obtained from the area touched
by a finger change to positive values. This allows for touching of
the touch panel 11 to be correctly detected.
[0044] Under the situation illustrated in FIG. 6A, when another
foreign matter (not illustrated) contacts the operation surface
11a, the newly obtained control data values change, for example, as
illustrated by the double-dashed line in FIG. 6C. Accordingly, the
control unit 24 determines from the control data values that
another foreign matter exists on the operation surface 11a and sets
each control reference value to the control data reference value,
that is, the same value as the capacitance corresponding to the
present control data value. When the capacitance of each capacitor
C is newly obtained under this situation, as illustrated by the
bold line in FIG. 6C, the control data value is zero. Accordingly,
if the touch panel 11 is touched when a foreign matter exists on
the operation surface 11a, the control data values obtained from
the area touched by a finger change to positive values. This allows
for touching of the touch panel 11 to be correctly detected.
[0045] FIG. 7A illustrates a situation in which a finger contacts a
foreign matter on the operation surface 11a. In this case, as
illustrated in FIG. 7B, the raw data values in the area in which
the finger and the foreign matter are located change to positive
values. In other words, the raw data values change in substantially
the same manner as when a large finger touches the operation
surface 11a. Under the situation illustrated in FIG. 7A, the raw
data values are greater than the foreign matter threshold.
Accordingly, the control unit 24 determines from the raw data
values that there is no foreign matter on the operation surface 11a
and sets each control reference value to the initial reference
value (refer to step S11 in FIG. 5). Consequently, as illustrated
by the bold line in FIG. 7C, the control data values newly obtained
each show the amount of change in the capacitance of the
corresponding capacitor C from the initial reference value. That
is, the control data values are the same as the raw data values. If
the control reference values were not set to the raw data reference
values, the control data values would be as illustrated by the
double-dashed line in FIG. 7C.
[0046] FIG. 8A illustrates a situation in which swiping is
performed with a finger that remains in contact with a foreign
matter. The finger and the foreign object move integrally with each
other on the operation surface 11a. Thus, referring to FIG. 8B, the
area in which the raw data values are positive changes as the
finger moves. Here, if the control reference values were to be set
to the raw data reference values, the control data values of the
area from which the foreign matter moves away on the operation
surface 11a would change in the same manner as when a foreign
matter or a finger contacts the operation surface 11a as
illustrated by the single-dashed line in FIG. 8C. In this regard,
in the present embodiment, when the control unit 24 detects the
touching of the touch panel 11 from the raw data values, the
control unit 24 resets the control reference values to the initial
reference values as described above. Thus, as illustrated by the
bold line in FIG. 8C, the control data values are the same as the
raw data values. As a result, a foreign matter is not erroneously
detected as being in contact with an area from which the foreign
matter has moved away. This allows for swiping of the touch panel
11 to be correctly detected.
[0047] The present embodiment has the advantages described
below.
[0048] (1) The control unit 24 changes the control reference value
for each capacitor C in accordance with whether or not a foreign
matter exists. Then, the control unit 24 obtains, as the control
data value, the amount of change in the capacitance of each
capacitor C from the corresponding control reference value. The
control unit 24 detects the touching of the touch panel 11 from the
control data values. Accordingly, even when a foreign matter
remains in contact with the operation surface 11a, the control unit
24 is able to correctly recognize changes in the capacitance when a
finger touches the operation surface 11a. This allows for the
touching of the touch panel 11 to be correctly detected. Further,
when the control unit 24 determines from the raw data values that a
foreign matter exists, the control unit 24 sets the control
reference values to the raw data reference values that are the same
as the present raw data values. When the control unit 24 determines
from the raw data values that there is no foreign matter, the
control unit 24 sets the control reference values to the initial
reference values. Thus, even when the touch panel 11 is swiped with
the finger remaining in contact with a foreign matter, the control
data values are not changed in an area of the operation surface 11a
from which the foreign matter has moved away. This allows for the
swiping to be correctly detected. In the present embodiment, the
touch type input device 5 is installed in the vehicle. When the
user is driving the vehicle, the user may not be able to readily
remove a foreign matter from the touch panel 11. Thus, the
structure according to the present embodiment improves the
convenience by allowing for the detection of a touch even when a
foreign matter is in contact with the operation surface 11a.
[0049] (2) When the control unit 24 determines from the raw data
values that a foreign matter exists, the control unit 24 further
determines from the control data values (newly obtained
capacitances) whether or not another foreign matter exists. Thus,
when a foreign matter comes into contact with the operation surface
11a, the control unit 24 is able to determine after a certain
period of time whether another foreign matter is in contact with
the operation surface 11a. Further, when the control unit 24
determines the existence of a foreign matter from the control data
values, the control unit 24 sets each control reference value to
the control data reference value that is the same as the present
control data value. On the other hand, when the control unit 24
determines from the control reference values that there is no
foreign matter, the control unit 24 sets each control reference
value to the raw data reference value, that is, the same value as
the present control reference value. Thus, even when different
foreign matters contact the operation surface 11a at different
timings, the control unit 24 is able to correctly recognize changes
in the capacitance of each capacitor C when a finger or the like
touches the operation surface 11a. This allows for the touching of
the touch panel 11 to be correctly detected.
[0050] It should be apparent to those skilled in the art that the
present invention may be embodied in many other specific forms
without departing from the spirit or scope of the invention.
Particularly, it should be understood that the present invention
may be embodied in the following forms.
[0051] In the above embodiment, the foreign matter determination
based on the control data values may be omitted. More specifically,
steps S7 to S9 may be omitted from the flowchart of FIG. 5. In this
case, whenever the control unit 24 determines the existence of a
foreign matter from the raw data values, the control unit 24 may
set the control reference value of each capacitor C to the raw data
reference value corresponding to the present raw data value.
[0052] In the above embodiment, the control unit 24 determines that
a foreign matter is existing when at least one of the raw data
values is less than or equal to the foreign matter determination
threshold. Instead, the control unit 24 may determine that a
foreign matter is existing when at least one of the raw data values
is less than or equal to a negative first foreign matter threshold
and at least another one of the raw data values is greater than or
equal to a positive second foreign matter threshold. This is
because the raw data values in the area in which a foreign matter
is existing change toward the negative side, and the raw data
values in the area around the foreign matter change toward the
positive side (see FIG. 6B). Further, other foreign matter
determination conditions may be used to perform foreign matter
determination. The foreign matter determination that is based on
the control data values may also be modified in the same manner.
Further, the condition for detecting the touching of the touch
panel 11 does not have to be at least one of the control data
values being greater than or equal to a touch determination
threshold.
[0053] In the above embodiment, when a foreign matter contacts the
operation surface 11a, the same values as the raw data values are
used as the raw data reference values. However, the raw data
reference values may be set in accordance with the raw data values
and do not have to be completely the same as the raw data values.
In the same manner, the control data reference values do not have
to be completely the same as the control data values when the
contact of a foreign matter with the operation surface 11a is
determined. Further, each initial reference value does not have to
be completely the same as the capacitance when there is no object
on the operation surface.
[0054] The present examples and embodiments are to be considered as
illustrative and not restrictive, and the invention is not to be
limited to the details given herein, but may be modified within the
scope and equivalence of the appended claims.
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